National broadband provider Primus is still considering whether to implement a voluntary internet service provider-based filter to stop customers reaching child pornography sites, despite making a commitment on the issue 12 months ago to the Federal Government.

The voluntary filtering initiative was a stop-gap measure agreed to by Telstra, Optus, Primus and the Federal Government in mid-2010 while a review was carried out into the Refused Classification category of content, which the government's wider mandatory filter project is slated to block. The internet service provider's (ISP) filter will only block sites with child pornography instead of those with illegal content in general.

Telstra and Optus have both reiterated their commitment to implementing the voluntary filter over the past week, with both ISPs' internal technical proposals on the matter believed to be well advanced. Primus said it was still deciding on the matter when asked this morning.

"At this stage iPrimus have no current plans to impose the voluntary filter on 1 July, only Telstra and Optus have announced they will," said Mick. "Yes, some media is reporting this, but they would be going on the fact we were part of the original three that were discussing it; however, iPrimus have made no official announcements to date or made a decision that we will be turning it on along with Telstra and Optus."

Mick said there had been "no word internally" to let staff know whether Primus' plans were going ahead. "...at this stage until something official comes out from Primus ... (and no the media is not an official source), I would take that as Primus are not filtering at this stage," he said.

The news comes as fresh revelations regarding the voluntary filter have come to light over the past few days.

On Saturday, Telstra revealed it was close to achieving executive sign-off for its internal proposal guiding the technical details of how it will cooperate with the voluntary filter project. In addition, although the original plan was to block a list of sites supplied by the Australian Communications and Media Authority, Telstra revealed that it is now planning to block a list provided by international policing body, Interpol. Optus is being asked for comment on its approach.

As the voluntary filtering regime comes closer to reality in Australia, with the ISPs planning to implement the system over the next few months, online rights campaigners have again begun to raise their voices in opposition to the idea.

Last week, global digital rights lobby group, the Electronic Frontiers Foundation, published a statement strongly opposing the voluntary filter, stating the plan lacked transparency in the selection of the internet addresses to be blocked, and a lack of accountability from regulatory bodies creating the blacklists. The Office of Communications Minister Stephen Conroy has said that the final details of the voluntary filter are still being worked through with ISPs.